Man, like all living creatures has to have sleep. Despite a great deal of research, the
purpose of sleep is not fully understood.
Sleep is a natural state of reduced consciousness involving changes in body and brain
physiology which is necessary to man to restore and replenish the body and brain.
Sleep can be resisted for a short time, but various parts of the brain ensure that
sooner or later, sleep occurs. When it does, it is characterised by five stages of sleep:
• Stage 1: This is a transitional phase between waking and sleeping. The heart rate
slows and muscles relax. It is easy to wake someone up.
• Stage 2: This is a deeper level of sleep, but it is still fairly easy to wake someone.
• Stage 3: Sleep is even deeper and the sleeper is now quite unresponsive to
external stimuli and so is difficult to wake. Heart rate, blood pressure and body
temperature continue to drop.
• Stage 4: This is the deepest stage of sleep and it is very difficult to wake someone
up.
• Rapid Eye Movement or REM Sleep: Even though this stage is characterised by
brain activity similar to a person who is awake, the person is even more difficult to
awaken than stage 4. It is therefore also known as paradoxical sleep. Muscles
become totally relaxed and the eyes rapidly dart back and forth under the eyelids.
It is thought that dreaming occurs during REM sleep.
Stages 1 to 4 are collectively known as non-REM (NREM) sleep. Stages 2-4 are
categorised as slow-wave sleep and appear to relate to body restoration, whereas
REM sleep seems to aid the strengthening and organisation of memories. Sleep
deprivation experiments suggest that if a person is deprived of stage 1-4 sleep or
REM sleep he will show rebound effects. This means that in subsequent sleep, he
will make up the deficit in that particular type of sleep. This shows the importance of
both types of sleep.
sleep occurs in cycles. Typically, the first REM sleep
will occur about 90 minutes after the onset of sleep. The cycle of stage 1 to 4 sleep
and REM sleep repeats during the night about every 90 minutes. Most deep sleep
occurs earlier in the night and REM sleep becomes greater as the night goes on. http://technique10465.blogspot.in/
purpose of sleep is not fully understood.
Sleep is a natural state of reduced consciousness involving changes in body and brain
physiology which is necessary to man to restore and replenish the body and brain.
Sleep can be resisted for a short time, but various parts of the brain ensure that
sooner or later, sleep occurs. When it does, it is characterised by five stages of sleep:
• Stage 1: This is a transitional phase between waking and sleeping. The heart rate
slows and muscles relax. It is easy to wake someone up.
• Stage 2: This is a deeper level of sleep, but it is still fairly easy to wake someone.
• Stage 3: Sleep is even deeper and the sleeper is now quite unresponsive to
external stimuli and so is difficult to wake. Heart rate, blood pressure and body
temperature continue to drop.
• Stage 4: This is the deepest stage of sleep and it is very difficult to wake someone
up.
• Rapid Eye Movement or REM Sleep: Even though this stage is characterised by
brain activity similar to a person who is awake, the person is even more difficult to
awaken than stage 4. It is therefore also known as paradoxical sleep. Muscles
become totally relaxed and the eyes rapidly dart back and forth under the eyelids.
It is thought that dreaming occurs during REM sleep.
Stages 1 to 4 are collectively known as non-REM (NREM) sleep. Stages 2-4 are
categorised as slow-wave sleep and appear to relate to body restoration, whereas
REM sleep seems to aid the strengthening and organisation of memories. Sleep
deprivation experiments suggest that if a person is deprived of stage 1-4 sleep or
REM sleep he will show rebound effects. This means that in subsequent sleep, he
will make up the deficit in that particular type of sleep. This shows the importance of
both types of sleep.
sleep occurs in cycles. Typically, the first REM sleep
will occur about 90 minutes after the onset of sleep. The cycle of stage 1 to 4 sleep
and REM sleep repeats during the night about every 90 minutes. Most deep sleep
occurs earlier in the night and REM sleep becomes greater as the night goes on. http://technique10465.blogspot.in/
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